A conventional semiconductor fabrication plant typically includes multiple fabrication areas or stations interconnected by a bay. Each station generally includes the requisite fabrication tools to provide a particular semiconductor manufacturing process, such as photolithography, chemical-mechanical polishing, chemical vapor deposition, etc.
In the semiconductor manufacturing processes described above, defect inspection is carried out in some manufacturing processes. In the defect inspection, the surface of the semiconductor wafer is inspected to see if there are scratches, dust, cracks, stains or uneven portions manually. Defects such as cracks may result in the breaking of the wafer itself. Therefore, the presence or absence of defects at the wafer edge portion has to be detected as early a step as possible to determine whether the wafer is good or bad.